I conjecture method calls contribute to the expense. Here is a way to eliminate
~~ half the calls for the inner loop:
(define (draw-to-dc dc)
(send dc set-pen no-pen)
(send dc set-brush brush-red)
(send dc draw-rectangle 0 0 XMAX YMAX)
(send dc set-brush brush-blue)
(for* ([x (in-range NUM-CELL-X)]
[y (in-range NUM-CELL-Y)]
#:when (= 0 (random 2)))
(send dc draw-rectangle (* x CELL-SIZE) (* y CELL-SIZE) CELL-SIZE
CELL-SIZE)))
It seems to run twice as fast but I don't have time to investigate. I am sure
more savings are possible here (generic?).
I do wonder whether the compiler coach could help here eventually. Relevant
people CCed.
-- Matthias
On Jul 16, 2015, at 12:15 PM, Laurent <laurent.ors...@gmail.com> wrote:
> I'm surprised by the slowness of animations in a canvas. Here's a simple
> stress test:
> https://gist.github.com/Metaxal/73897e7bac5332054511
>
> For a 100x100 board it takes 2 seconds to draw 10 random frames (outside
> DrRacket of course). I was expecting at least 10x more frames per second.
>
> Is there anything that could speed this up substantially?
>
> Some notes:
> - Using bigger cells (say size 10 instead of 2) has only a small impact on
> the performance
> - Drawing directly to the canvas instead of using an intermediate buffer
> doesn't help (it's actually even worse because `refresh` may be called more
> than necessary)
> - Replacing for* by let loops with additions and no multiplication makes no
> difference
> - Creating the brushes outside the for loop is much faster (almost 1/3) than
> inside
> - `draw-point` is quite slower than `draw-rectangle` for some reason
> - displaying a random number in the terminal instead of selecting the brush
> and drawing the rectangle is twice faster
> - I'm on Ubuntu 14.04, racket 6.1.1, 64bits
>
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